The assembly of sheet stock, whether metal, plastic or some other material, into various structures such as boxes, cages, covers, etc. requires some method of fastening those elements together in order to form those structures. Typical fastening methods include the use of flanges, connected by rivets or screws, standoffs, and tapped elements welded or riveted to flat areas of the assembly components. However, the use of flanges requires an unnecessary waste of space. An example of such wasted space occurs when a flange is mounted to a circuit board thereby eliminating use of the underlying printed circuit board area. Such flanges are typically mounted to a printed circuit board in order to mount a radio frequency shield to that board via the flange. Standoffs and tapped elements, welded to the assemblies, are also expensive and create an awkward assembly package. Plastic parts, tapped or drilled for self tapping screws, have also been used.
Alternative fastening methods include the use of circular plastic parts, tapped or drilled for self tapping screws. These parts have a spring-like section on their circumference which is deflected when they are pressed into an opening in an assembly panel. When so pressed a sufficient distance into such an opening the spring-like section is released and returns to its normal position, thereby locking the part in place. However, these parts, which are expensive, are subject to cold flow distortion do not conduct current and tend to become loose over a period of years.
Another fastening method is described in U.S. Pat. No. 3,967,432 which was issued to V. B. Starr on July 6, 1976. However, the fastener disclosed in that patent was of a complex design.